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-   -   Intake manifold movement? (http://986forum.com/forums/boxster-general-discussions/65682-intake-manifold-movement.html)

WillH 03-06-2017 05:16 PM

Intake manifold movement?
 
Noticed what appears to be the manifolds moving away from each other as throttle is given. Or am I just seeing the throttle body moving upwards , (being held by intake tube), as the engine rotates to the passenger side in response to the torque?
Did I miss a passage about variable intake lengths that require manifold movement?

Gelbster 03-06-2017 06:27 PM

If the engine is moving like that - have you checked the engine mounts?

WillH 03-07-2017 01:53 AM

Engine mount only has a few thousand miles on it. It's the normal amount of movement that I would expect to see on any rubber mounted engine and less than what you normally get with a v8. Are the manifolds flexible?

alm001 03-07-2017 05:37 AM

This happens on mine. The boots between the manifolds are rubber, and under vacuum they will contract.

Gilles 03-07-2017 05:42 AM

Will is saying that the intake manifolds are moving away from each other ?, this means that one of them could be loose, but if you have a worn engine/tranny mount both manifolds will move along with the throttle body (and engine..)

alm001 03-07-2017 05:48 AM

Quote:

Originally Posted by Gilles (Post 529390)
Will is saying that the intake manifolds are moving away from each other ?, this means that one of them could be loose, but if you have a worn engine/tranny mount both manifolds will move along with the throttle body (and engine..)

Right, moving away from each other under throttle. So as he presses the throttle manifold vacuum level goes down, and the manifolds move apart.

WillH 03-07-2017 01:58 PM

https://youtu.be/8_ADUbIiaP0
Sorry I can't embed for some reason...

WillH 03-08-2017 02:51 AM

I'll find the torque value for the manifold bolts and give them a check on Friday. I would assume that if they were that loose to allow movement that it would throw a code...

Gilles 03-08-2017 07:09 AM

Quote:

Originally Posted by WillH (Post 529521)
I'll find the torque value for the manifold bolts and give them a check on Friday. I would assume that if they were that loose to allow movement that it would throw a code...

Will, I would also check the engine and gearbox supports.

WillH 03-08-2017 02:53 PM

Quote:

Originally Posted by alm001 (Post 529388)
This happens on mine. The boots between the manifolds are rubber, and under vacuum they will contract.

So does yours react the same as my video? Can't figure out if this is trompe l'oeil or if there is an issue here. I'll take measurements at rest and under vacuum...
Friday or Saturday morning...

Ben006 03-08-2017 03:34 PM

It's normal.

At idle you're at 26inHg of vaccum inside the manifold, and when you open the throttle, you have almost atmospheric pressure.
This difference of pressure added with the design of the manifold (distance between manifold mounting flange and plenum) makes the whole thing move.

That's why the guys that went with forced induction have to strap the manifolds together ;)

And also why Porsche is using a plenum with spin-locks and tie bar on all the last generation 911 with turbos!

IMGP3367.jpg Photo by caseyparkin | Photobucket

WillH 03-08-2017 03:55 PM

Quote:

Originally Posted by Ben006 (Post 529589)
It's normal.

At idle you're at 26inHg of vaccum inside the manifold, and when you open the throttle, you have almost atmospheric pressure.
This difference of pressure added with the design of the manifold (distance between manifold mounting flange and plenum) makes the whole thing move.

That's why the guys that went with forced induction have to strap the manifolds together ;)

And also why Porsche is using a plenum with spin-locks and tie bar on all the last generation 911 with turbos!

IMGP3367.jpg Photo by caseyparkin | Photobucket

Many thanks Ben :cheers:


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